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Discussion Starter #1
Newbie here, but I have been searching all over the place the last few weeks and couldn't find any answers so I'm hoping you guys can help. I'm building a race car that will have a stand alone engine harness and computer so I have been going through a trying to thin out the entire body harness. The car is a 90 4 cylinder 5spd coupe. I have been able to slowly get a lot of wiring out from the dash harness and the body harness but have a few questions still. First main question would be can I use a 1990 v8 headlight harness? (this car never had a headlight harness when I bought it) I know that the alternator plug will be on the opposite side but I really only need the harness to run the lights, no alt plugs are needed, I also won't be using the washer fluid tank or pump, also won't have any other sensors for the coolant overflow needed either. My concern is where it will get the 12v from since I believe the 4 cyl dash harness has the main power feed (multiple yellow wires tied together) for the alternator. Just want to know if this is possible to use the v8 headlight harness or not with the 4 cyl dash harness. I have a few other questions also regarding the part of the dash harness that goes out into the engine bay, can I completely cut out the 2 plugs that I believe plugged into the engine harness? I have these plugs down to only having about 2 wires in each as I already tried to cut out as much of the engine wiring from the dash wiring (ie. oil pressure sender, coolant temp, etc) and this left me with a few wires in each plug still. I'll post some pics here shortly from my phone.
 

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Discussion Starter #3
Some other engine bay dash harness plugs I wasn't sure of are the 2 plugs with plug ends installed in them, the first 2 pictures are the plugs that have factory plug ends stuck in them and am not sure what they do. The 3rd picture I'm not sure what that piece is, one the wires then goes to the plug in the 2nd pic. The 4th pic is of the 2 plugs that I believe went into the factory engine harness, the cut wires are from where I already removed inputs to the cluster such as oil pressure, temp, etc, I was able to find the cluster diagram and cut out those inputs since they won't be used with that harness, but there are still a few wires in those plugs I need to trace back and see if they are needed. The 5th pic is the 2 plugs that then plug into the headlight harness, I'm a little concerned since the smaller of the 2 plugs I already removed 2 of the wires and its only has 1 left going into it. The last picture is what I believe to be the wire that would get attached to the alt (yellow) the one beside it I don't know. There is also another set of wires that goes into a ring terminal that appears to be a ground? Any advice for me here? Thanks for any input you guys can give.
 

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you are best to get the proper wiring diagrams to ID the circuits.

I doubt anybody has this info memorized, or is going to do all the leg work for you.
 

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Discussion Starter #5
so no one else has done this before? BTW I haven't been able to find a diagram that tells me what the plugs are within the dash and body wiring diagram, only the computer which I don't care about. Does anyone atleast know what the plugs with plug ends inserted into them are that are in the drivers side fender?
 

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helm publication

has what you need

called EVTM
 

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Discussion Starter #7
Well without getting a helm EVTM manual I was able to figure out the big plug in the first pic is apparently for DRL and on canadian models a module gets plugged in there and the US models get that cap put in place. Has anyone ever cut these wires out to simplify the harness? Also can anyone confirm if the plug in the 2nd pic is for the washer tank? Or if the use of a 90 v8 headlight harness can be used with a 4 cylinder dash harness?
 
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